Shallow trench isolation methods and corresponding structures are disclosed. According to one embodiment (900) a nitride layer (1006), having an opening (1014), is formed over a silicon substrate (1002). The portion of the substrate (1002) below the opening (1014) is oxidized to form a substrate consuming rounding oxide layer (1018). The formation of the rounding oxide layer (1018) results in rounded edges in the substrate (1002). An isotropic, or alternatively, an anisotropic rounding oxide etch removes the rounding oxide layer (1018) to expose the substrate (1002). A trench (1026) can be formed by applying a silicon etch using the nitride layer (1006) as an etch mask. The trench (1026) can be subsequently filled with a deposited trench isolation material (1030).
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method of forming an isolation structure in a substrate, the method comprising the steps of: etching a barrier layer to form at least one barrier opening; forming a substrate consuming layer below the at least one barrier opening that includes a top surface that extends above the substrate top surface; isotropically etching at least a portion of the substrate consuming layer to form a top portion of an isolation trench in the substrate, the isolation trench electrically isolating active devices from one another; removing a second portion of the substrate to form a bottom portion of the isolation trench below the top portion of the trench; depositing an isolation material in the trench; and planarizing a resulting surface so that a top surface of the isolation material is substantially even with a top surface of the substrate.
2. The method of claim 1 , further including: forming the barrier layer over the substrate.
3. The method of claim 2 , wherein: the stop of forming a barrier layer includes depositing a layer of silicon nitride and etching at least one opening in the layer of silicon nitride.
4. The method of claim 3 , wherein: the step of forming a barrier layer further includes etching the surface of the substrate disposed below the at least one opening and forming a gouge in the surface of the substrate.
5. The method of claim 1 , wherein: the step of forming a substrate consuming layer includes oxidizing a portion of the substrate below the at least one opening.
6. The method of claim 5 , wherein: the step of oxidizing a portion of the substrate forms rounded edges in the surface of the substrate.
7. The method of claim 5 , wherein: the substrate includes silicon; and the stop of oxidizing a portion of the substrate includes forming a layer of silicon dioxide having lateral extents that are limited by the at least one opening in the barrier layer.
8. The method of claim 1 , wherein: the step of removing the second portion of the substrate includes substantially anisotropically etching the substrate.
9. The method of claim 8 , wherein: the substrate consuming layer includes silicon dioxide having encroaching portions that extend below edges of the at least one opening; isotropically etching at least a portion of the substrate consuming layer substantially removes the encroaching portions.
10. The method of claim 1 , wherein: the substrate includes silicon; and the step of forming the top portion of the isolation trench includes etching selectively the substrate while the barrier layer remains over the substrate.
11. The method of claim 1 , wherein: the substrate include silicon; and the step of depositing an isolation material includes depositing silicon dioxide from a high density plasms.
12. The method of claim 11 , further comprising densifying the deposited silicon dioxide.
13. The method of claim 1 , further including: planarizing the resulting surface.
14. The method of claim 13 , wherein: the step of planarizing includes chemical-mechanical polishing.
15. The method of claim 1 , further including: depositing an isolation material into the isolation trench.
16. The method of claim 1 , wherein: the stop of isotropically etching at least a portion of the substrate consuming layer includes wet chemically etching the substrate consuming layer.
17. A method of shallow trench isolation comprising the steps of: forming a barrier layer having at least one opening; oxidizing a silicon containing substrate to form a layer of silicon dioxide below the at least one opening, the silicon dioxide extending into the substrate and having rounded corners; anisotropically etching at least a portion of the silicon dioxide layer below the at least one opening to form a gouge in the substrate, the gouge having rounded edges and residual portions of the silicon dioxide layer above the rounded edges; forming an isolation trench in the silicon substrate within the gouge to a depth substantially deeper than the gouge, the rounded edges of the gouge forming top edges for the isolation trench, the isolation trench electrically isolating active devices from one another; filling the isolation trench with an isolation material; and planarizing a resulting surface so that a top surface of the isolation material is substantially even with a top surface of the substrate.
18. The method of claim 17 wherein: the step of forming the isolation trench includes etching the substrate with the barrier layer in place over the substrate.
19. A shallow trench isolation (STI) structure, comprising: an isolation trench formed in a silicon substrate that electrically isolates active devices from one another, the isolation trench including a rounded trench edge formed by oxidizing the silicon substrate that joins a side surface of the trench with a top surface of the silicon substrate, the side surface of the isolation trench being a silicon-etched side surface formed by etching the silicon substrate after oxidizing the silicon substrate; and a trench isolation layer formed within the isolation trench adjacent to the rounded trench edge and the trench side surface having a top surface that is substantially even with a top surface of the substrate, the trench isolation layer including an isolation encroaching portion extending toward a top silicon substrate surface from the rounded trench edge and essentially coplanar with the top silicon substrate surface, the isolation encroaching portion formed from oxidized silicon substrate material.
20. The STI structure of claim 19 , wherein: the trench isolation layer comprises deposited high density plasma silicon dioxide.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
December 9, 1998
November 30, 2004
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